Project Statement
The NE Siskiyou Green Street is regarded
as one of Portland’s best green street stormwater
retrofit examples. The first of its kind anywhere, this
project replaces the parking zone of a typical residential
street with landscaped stormwater curb extensions designed
to capture street stormwater runoff. Built in the fall
of 2003, the NE Siskiyou Green Street project exemplifies
the principles of sustainable stormwater management
and showcases the value of simple, cost effective, and
innovative design solutions.
Narrative Summary
The NE Siskiyou Green Street project is
unique to Portland and the United States in the way
this quiet, 80 year-old residential street has been
transformed to sustainably manage its stormwater runoff.
As part of the City of Portland’s commitment to
promote a more natural approach to urban stormwater
management, this “green street” project
carves out a portion of the street’s parking zone
and converts it into two landscaped curb extensions.
Conventional curb extensions are often used for traffic
calming and pedestrian safety. The curb extensions at
NE Siskiyou Street share many of the same benefits of
conventional curb extensions, however they are different
in that they are also designed to elegantly capture,
slow, cleanse, and infiltrate street runoff. Constructed
in the fall of 2003, this street retrofit project demonstrates
how both new and existing streets can be designed to
provide direct environmental benefits and be aesthetically
integrated into the neighborhood streetscape. Though
this green street project maintains a strong functional
component, it is the aesthetic appeal and intrigue of
the new and improved NE Siskiyou Street that has the
design community, developers, policy makers, and local
citizens excited about green street design opportunities.
Since its completion in 2003, the NE Siskiyou Green
Street project has been a successful “catalyst”
project by providing inspiration for the development
of other green street projects throughout the United
States.
How does the NE Siskiyou Green
Street Work?
The NE Siskiyou Green Street project
essentially disconnects the street’s rainwater
runoff from the City’s combined storm/sewer pipe
system and manages it on-site using a landscape approach.
Stormwater runoff from 10,000 square feet of NE Siskiyou
Street and neighboring driveways flows downhill along
the existing curb until it reaches the 7-foot wide,
50-foot long curb extensions. An 18-inch wide curb cut
allows this water to enter each curb extension. Once
water is within the landscape area, the water is retained
to a depth of 7 inches by a series of checkdams. Depending
on the intensity of a rain event, water will cascade
from one "cell" to another until plants and
soil absorb the runoff or until the curb extensions
reach their storage capacity. The landscape system in
place infiltrates water at a rate of 3 inches per hour.
If a storm is intense enough, water will exit the landscape
area through another curb cut at the end of each curb
extension and will flow into the existing street inlets.
With the new stormwater curb extensions now in place,
nearly all of NE Siskiyou’s annual street runoff,
estimated at 225,000 gallons, is managed by its landscape
system. In fact, multiple simulated flow tests have
shown that the curb extensions at NE Siskiyou Street
have the ability to reduce the runoff intensity of a
typical 25-year storm event by 85 percent. Where communities
struggle with ever-increasing impervious areas and degraded
water quality, these simple landscape approaches can
have a measurable positive impact.
The Planting is the Key
Plants and soil are key functional
elements of all landscaped stormwater facilities. This
natural system approach improves the quality of the
urban runoff through bio-retention processes and helps
restore lost hydrologic functions in urbanized areas.
The plants selected for the NE Siskiyou Green Street
are primarily Pacific Northwest natives, such as Oregon
grape, sword fern, and grooved rush. Adaptable ornamental
species such as blue oat grass, boxleaf euonymus, and
New Zealand sedge, were also planted because these species
are low-maintenance and fit very well in the neighborhood
context. All of the selected plant species are low-growing
evergreen varieties with varying colors and textures
which always provide year-round interest. The native
grooved rush (Juncus patens) planted within the shallow
areas of each stormwater curb extension is the workhorse
for stormwater management. The upright growth structure
of Juncus patens slows down water flow and captures
pollutants while its deep penetrating roots work well
for water absorption. The highlight for NE Siskiyou
Street residents each year comes at springtime when
they see a collage of both daffodils and iris species
blooming within the stormwater curb extensions, just
as they do in their own front yards.
Special Design Considerations
and Project Goals
Because The NE Siskiyou Green Street
Project was the first of its kind, the design, coordination,
and permitting with other City Bureaus took almost a
year to complete. Public outreach to the residents was
extensive to assure acceptability and consensus. The
effort has paid off in terms of widespread community
acceptance. In fact, the City now has a waiting list
of Portland residents who want similar landscaped stormwater
facilities built on their own streets. The fact that
this is a publicly designed and constructed facility
provides a unique opportunity to bring government together
with its citizens in a creative and positive partnership.
The NE Siskiyou Green Street project has achieved three
primary goals: 1) it is low-cost in its design and execution;
2) it benefits the environment and embodies community
livability; and 3) it provides a model for other jurisdictions
in addressing important national and local stormwater
regulations. These landscaped stormwater curb extensions
are beautiful to look at and bring natural hydrologic
functions back into the city. However to be a viable
tool for innovative stormwater management, the NE Siskiyou
Green Street Project needed to be relatively simple
to construct, as maintenance friendly as possible, and
cost effective. Using stormwater checkdams made out
of packed earth covered with river rock is one example
of a simple, attractive, and environmentally sustainable
design element that costs very little to install. Cost
effective solutions such as these allowed the project
to be built for under $20,000.
Community Involvement
The success of neighborhood stormwater projects like
the NE Siskiyou Green Street is dependent on community
involvement. The residents were active participants
in the design process. Multiple "street side chats"
were conducted during the summer of 2003 to determine
how much parking to remove and what planting schemes
they desired, as well as to answer any questions and
address any concerns. Communication with the neighbors
continues to this day in the form of surveys and site
visits to determine the overall success of the project
from the neighborhood perspective.
In a unique partnership, the City and
the neighborhood residents have agreed to share responsibilities
in maintaining the landscaped stormwater curb extensions.
To further engage the community, a small interpretative
sign has been placed at the project site to describe
how the stormwater facilities function, as well as how
to find more information on sustainable stormwater management
practices.
The aesthetic appeal and intrigue
of the new stormwater facilities creates a community
asset that promotes both environmental stewardship and
education at the neighborhood level. The NE Siskiyou
Green Street project has caught the attention Portland
locals as well as visitors from all over the United
States, Europe, and Asia who find this small retrofit
project as an example to follow.
|
